Add the following at the end of your ~/.bashrc (Linux) or ~/.bash_profile (macOS) file.
1# Case-insensitive Tab auto-complete
2$include /etc/inputrc
3set completion-ignore-case on
You may get a Permission denied error. In that case just add it to the system-wide file
1sudo nano /etc/inputrc
Add the following at the end of the file
1# Case-insensitive Tab auto-complete
2set completion-ignore-case on